Zeroth & First Law of Thermodynamics — Practice Questions

Free NEET Physics multiple-choice questions on Zeroth & First Law of Thermodynamics. Attempt each question and reveal the answer with a full explanation.

For which of the following reactions, the value of H is equal to U ? H 2(g) + I 2(g) 2HI(g) N 2(g) + 3H 2(g) 2NH 3(g) PCl 5(g) PCl 3(g) + Cl 2(g) 2SO 2(g) + O 2(g) 2SO 3(g) Which relation represents the first law of thermodynamics for an isochoric process? U = q U = w q = -w H = q Which of the following describes the 'Coefficient of Volume Expansion' ( ) for an ideal gas at constant pressure? = 1/T = T = 1/P = P/T If a gas mixture contains 1 mole of a monoatomic gas and 1 mole of a diatomic gas, the effective ( C p/C v ) for the mixture is: 1.5 1.67 1.4 1.33 The heat required to raise the temperature of 1 mole of a monoatomic gas from 25 C to 35 C at constant pressure is: 25R 15R 30R 5R For the phase transition Liquid Vapor at its boiling point, which of the following is true? G = 0 S = 0 H = 0 U = 0 The heat capacity of a substance at constant pressure ( C p ) and constant volume ( C v ) are related by the equation: C p - C v = R C v - C p = R C p / C v = R C p + C v = R Under which condition is the change in enthalpy ( H ) equal to the heat supplied to the system? At constant pressure At constant volume At constant temperature In an adiabatic process According to the Hess's Law, the heat of a reaction depends on: Initial and final states of the reactants and products The path followed by the reaction The number of intermediate steps The physical state of the catalyst Which property of a system is independent of the amount of substance present? Temperature Volume Enthalpy Entropy A system absorbs 500 J of heat and does 200 J of work on the surroundings. What is the change in internal energy ( U ) of the system? +300 J +700 J -300 J -700 J Which of the following is not a state function? q + w q H S When 1 mole of gas is heated at constant volume, the temperature is raised from 298 K to 308 K. Heat supplied to the gas is 500 J. Which of the following is correct? q = w = 500 J, U = 0 q = U = 500 J, w = 0 q = w = 0, U = 500 J U = 0, q = w = -500 J Standard molar enthalpy of formation of CO is -110.5 kJ mol -1 and that of CO 2 is -393.5 kJ mol -1 . The enthalpy of combustion of CO is: -283.0 kJ mol -1 -504.0 kJ mol -1 +283.0 kJ mol -1 +504.0 kJ mol -1 A system is provided 50 J of heat and the change in internal energy is found to be 20 J. The work done by the system is: 30 J 70 J -30 J 50 J The internal energy of an ideal gas depends only on its: Temperature Pressure Volume Density The molar heat capacity of a gas at constant volume is C v . If n moles of the gas undergo T change in temperature, the heat exchanged at constant volume is: nC v T nC p T U + P V nRT For a monoatomic gas, the ratio of molar heat capacities = C p/C v is: 1.67 1.40 1.33 1.50 Standard molar enthalpy of formation of CO 2 is equal to: Standard molar enthalpy of combustion of carbon (graphite) Standard molar enthalpy of combustion of gaseous carbon Standard molar enthalpy of combustion of CO Zero The heat of neutralization of a strong acid and a strong base is nearly constant at: -57.1 kJ/mol -13.7 kJ/mol -25.5 kJ/mol -100 kJ/mol A system undergoes a process in which E = +300 J while absorbing 400 J of heat. The work done by the system is: 100 J 700 J -100 J -700 J Which of the following is correct for an isothermal expansion of an ideal gas? U = 0 H 0 q = 0 w = 0 The enthalpy of formation of ammonia is -46.0 kJ/mol . The enthalpy change for the reaction 2NH 3(g) N 2(g) + 3H 2(g) is: 92.0 kJ -46.0 kJ 46.0 kJ -92.0 kJ The difference between C p and C v is equal to R for: Ideal gas Real gas at high pressure Liquids Solids A system does 200 J of work and 600 J of heat is supplied to it. The change in internal energy is: 400 J 800 J -400 J -800 J The enthalpy of atomization of CH 4 is 1665 kJ/mol . The bond enthalpy of the C-H bond is: 416.25 kJ/mol 1665 kJ/mol 832.5 kJ/mol 555 kJ/mol For an ideal gas, the change in internal energy ( U ) for any process depends ONLY on: Change in temperature Change in pressure Change in volume Path followed by the system The heat absorbed by a system at constant volume ( q v ) is equal to: Change in internal energy ( U ) Change in enthalpy ( H ) Work done ( W ) Change in entropy ( S ) The internal energy change when a system goes from state A to B is 40 kJ/mol . If the system goes from A to B by a reversible path and returns to A by an irreversible path, what would be the net change in internal energy? Zero 40 kJ/mol 80 kJ/mol > 40 kJ/mol For a monoatomic gas, the molar heat capacity at constant pressure is: 5 2 R 3 2 R 1 2 R 3R The enthalpy of formation of all elements in their standard states is: Zero Positive Negative Depends on temperature An ideal gas expands from 1 L to 10 L in an isothermal reversible process at 300 K . What is the change in internal energy ( U )? 0 J 2.303 RT (10) -2.303 RT (10) RT (10) The bond enthalpy of C-C , C=C and C C bonds follow the trend: C C > C=C > C-C C-C > C=C > C C C=C > C C > C-C C C > C-C > C=C If the heat capacity of a calorimeter is 10 kJ/K , and the temperature of the water in it rises by 2.5 K upon combustion of a substance, the heat evolved is: 25 kJ 4 kJ 0.25 kJ 12.5 kJ Identify the state function among the following: Internal Energy Heat Work Both Heat and Work During the isothermal expansion of an ideal gas, which of the following remains constant? Internal Energy Pressure Volume Entropy The Zeroth Law of Thermodynamics is used to define which physical quantity? Temperature Internal Energy Entropy Enthalpy In a P-V diagram, the work done during a cyclic process is represented by: The area enclosed by the cycle The area under the P -axis The area under the V -axis The total length of the path A thermodynamic system undergoes a process in which its internal energy decreases by 500 J and it does 200 J of work. The heat exchange involved is: 300 J released 300 J absorbed 700 J released 700 J absorbed For a non-linear triatomic gas molecule, the number of degrees of freedom is: 6 3 5 7 The internal energy of 1 mole of an ideal gas depends on: Temperature only Volume only Pressure only Molecular size only For the reaction NH 4HS(s) NH 3(g) + H 2S(g) , the value of H - U at temperature T is: 2RT RT -2RT Zero According to the Dulong-Petit law, the molar heat capacity of most solid elements at room temperature is approximately: 3R R 3/2 R 5/2 R The standard enthalpy of formation of H +(aq) in water is taken by convention to be: 0 kJ/mol -286 kJ/mol +100 kJ/mol Variable depending on concentration For the reaction C(s) + 1/2 O 2(g) CO(g) , the difference H - U is: 0.5 RT RT -0.5 RT 1.5 RT Under standard conditions, the state of Bromine is defined as: Br 2(l) Br 2(g) Br(g) Br 2(s) The enthalpy of sublimation of a substance is equal to: Δ H fusion + Δ H vaporization Δ H fusion - Δ H vaporization Δ H vaporization - Δ H fusion Δ H fusion × Δ H vaporization For an ideal gas, the heat capacity at constant pressure ( C p ) is 7/2 R . The gas is most likely: Diatomic Monoatomic Triatomic non-linear A noble gas For a real gas, the Joule-Thomson coefficient is zero at: Inversion temperature Boyle temperature Critical temperature Absolute zero If the enthalpy of formation of H 2O(l) is -285.8 kJ/mol , what is the enthalpy change for the reaction 2H 2O(l) 2H 2(g) + O 2(g) ? +571.6 kJ -571.6 kJ +285.8 kJ -285.8 kJ The enthalpy of solution of NaOH in water is -44.5 kJ/mol . When NaOH is dissolved in water, the temperature of the solution: Increases Decreases Remains constant First increases then decreases The standard enthalpy of formation of NH 3(g) is -46.1 kJ mol -1 . What is the enthalpy change for the reaction: 2NH 3(g) N 2(g) + 3H 2(g) ? +92.2 kJ mol -1 -92.2 kJ mol -1 +46.1 kJ mol -1 -46.1 kJ mol -1 Which of the following is the standard state of phosphorus at 298 K and 1 bar ? P 4 (white) P 4 (red) P 4 (black) P 1 (monatomic) Consider the following graph of Pressure vs Volume for a cyclic process. The net work done is: The area enclosed by the loop The slope of the line Zero Sum of work in individual steps only The internal energy change in a system that has absorbed 2 k cal of heat and done 500 J of work is : 7900 J 8900 J 6400 J 5400 J An electric heater supplies heat to a system at a rate of 100 W. If the system performs work at a rate of 75 J/s, then the rate at which internal energy increases will be: 75 W 25 W 100 W 125 W Consider the reaction: N 2(g) + 3H 2(g) 2NH 3(g) , H = -92.4 kJ . What is the standard enthalpy of formation of NH 3(g) ? -46.2 kJ/mol -92.4 kJ/mol +46.2 kJ/mol +92.4 kJ/mol The internal energy of n moles of an ideal gas is given by U = f 2 nRT . For a monoatomic gas, the internal energy is purely: Translational kinetic energy Rotational kinetic energy Vibrational kinetic energy Potential energy For the reaction C(graphite) + O 2(g) CO 2(g) , which of the following is true? H = U H > U H < U H = 0 Which of the following is correct for a cyclic process? U = 0 H = 0 w = -q All of these Which of the following is true for an isothermal expansion of an ideal gas into vacuum? q = 0, w = 0, U = 0 q 0, w = 0, U = 0 q = 0, w 0, U = 0 q = 0, w = 0, U 0 For the process H 2O(l) H 2O(g) at 100 C and 1 atm pressure, the correct set of thermodynamic parameters is: G = 0, S > 0, H > 0 G = 0, S < 0, H < 0 G < 0, S > 0, H > 0 G > 0, S > 0, H > 0 The heat of combustion of carbon to CO 2 is -393.5 kJ/mol . The heat released upon formation of 35.2 g of CO 2 from carbon and oxygen gas is: 314.8 kJ 393.5 kJ 630 kJ 44 kJ The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are -890.3 kJ mol -1 , -393.5 kJ mol -1 and -285.8 kJ mol -1 respectively. Enthalpy of formation of CH 4(g) will be: -74.8 kJ mol -1 -52.2 kJ mol -1 +74.8 kJ mol -1 +52.2 kJ mol -1 The molar heat capacity of water at constant pressure, C p , is 75 J K -1 mol -1 . When 1.0 kJ of heat is supplied to 100 g of water which is free to expand, the increase in temperature of water is: 2.4 K 1.2 K 4.8 K 0.24 K The heat of formation of CO(g) and CO 2(g) are -110 and -393 kJ mol -1 respectively. What is the heat of combustion of CO(g) ? -283 kJ mol -1 +283 kJ mol -1 -503 kJ mol -1 -110 kJ mol -1 One mole of an ideal monoatomic gas is heated at constant pressure from 0 C to 100 C . Then the change in the internal energy of the gas is ( R = 8.32 J mol -1 K -1 ): 12.48 10 2 J 20.8 10 2 J 8.32 10 2 J 4.25 10 2 J Which of the following is an intensive property? Electromotive force (EMF) Entropy Enthalpy Volume The integral enthalpy of solution of KCl is +18.4 kJ/mol . This means the dissolution process is: Endothermic Exothermic Athermal Spontaneous only at low temperatures If the heat of formation of NO 2 is 33.2 kJ/mol , the heat of the reaction 2NO 2(g) N 2(g) + 2O 2(g) is: -66.4 kJ 66.4 kJ -33.2 kJ 33.2 kJ The enthalpy of neutralization of HCN by NaOH is -12.1 kJ/mol . The enthalpy of ionization of HCN is ( Heat of neutralization of strong acid/base = -57.1 kJ/mol ): 45.0 kJ/mol -45.0 kJ/mol 69.2 kJ/mol -69.2 kJ/mol The heat of formation of H 2O(l) is -285.8 kJ/mol . The heat of formation of H 2O(g) is -241.8 kJ/mol . The heat of vaporization of water per mole is: 44.0 kJ -44.0 kJ 527.6 kJ -527.6 kJ For which of the following reactions is the value of ( H - U) equal to -RT at temperature T ? NH 3(g) + HCl(g) NH 4Cl(s) H 2(g) + I 2(g) 2HI(g) PCl 5(g) PCl 3(g) + Cl 2(g) 2SO 2(g) + O 2(g) 2SO 3(g) The molar heat capacity of a diatomic gas at constant volume ( C v ) including vibrational degrees of freedom (at high temperature) is: 7 2 R 5 2 R 3 2 R 3R If the enthalpy of combustion of graphite is -393.5 kJ mol -1 and that of diamond is -395.4 kJ mol -1 , the enthalpy change for the transition C(graphite) C(diamond) is: +1.9 kJ mol -1 -1.9 kJ mol -1 +788.9 kJ mol -1 -788.9 kJ mol -1 According to the Kirchoff's equation, the variation of H of a reaction with temperature is given by: ( H / T) P = C p ( H / T) V = C v ( H / T) P = U ( H / P) T = C p The heat of formation of PCl 5(g) is -398.9 kJ/mol and that of PCl 3(g) is -306.4 kJ/mol . The H for the reaction PCl 5(g) PCl 3(g) + Cl 2(g) is: +92.5 kJ/mol -92.5 kJ/mol +705.3 kJ/mol -705.3 kJ/mol In which of the following reactions, is H not equal to U ? PCl 5(g) PCl 3(g) + Cl 2(g) H 2(g) + I 2(g) 2HI(g) C(s) + O 2(g) CO 2(g) N 2(g) + O 2(g) 2NO(g) The molar heat capacity of an ideal gas at constant pressure ( C p ) and constant volume ( C v ) are 20.8 and 12.5 J K -1 mol -1 respectively. The gas is most likely: Monoatomic Diatomic Triatomic linear Triatomic non-linear In a Bomb Calorimeter, the heat measured ( q v ) represents the change in: Internal Energy ( Δ U ) Enthalpy ( Δ H ) Gibbs Free Energy ( Δ G ) Entropy ( Δ S ) Which statement correctly describes the work done in a cyclic process? The net work done is equal to the area enclosed by the cycle on a P-V diagram The net work done is always zero The net work done is equal to the change in internal energy The net work done is equal to P V The enthalpy of neutralization of NaOH with HCl is -57.3 kJ/mol and with CH 3COOH is -55.2 kJ/mol . The enthalpy of ionization of CH 3COOH is: 2.1 kJ/mol -2.1 kJ/mol -112.5 kJ/mol 112.5 kJ/mol The molar heat capacity of a diatomic gas at constant volume is C v . If we consider the vibrational mode to be active, the value of C v is: 7/2 R 5/2 R 3/2 R R One mole of an ideal gas at an initial temperature of T K does 6R joules of work adiabatically. If the ratio of specific heats of this gas is 5/3 , the final temperature of the gas will be: (T - 4) K (T + 4) K (T - 2.4) K (T + 2.4) K The change in entropy when 10 g of ice at 0 C is converted into water at 0 C is: (Latent heat of fusion = 80 cal/g ) 2.93 cal/K 0.293 cal/K 800 cal/K 80 cal/K Which of the following expressions represents Kirchhoff's Law regarding the variation of enthalpy of reaction with temperature at constant pressure? H T 2 = H T 1 + C p(T 2 - T 1) U T 2 = U T 1 + C v(T 2 - T 1) H T 2 = H T 1 + C v(T 2 - T 1) G T 2 = G T 1 + S(T 2 - T 1) Calculate the entropy change for the fusion of 10 g of ice at 273 K . (Latent heat of fusion = 80 cal/g ) 2.93 cal/K 800 cal/K 0.34 cal/K 218.4 cal/K The fundamental thermodynamic relation for the change in internal energy dU of a system involving only P-V work is given by: dU = TdS - PdV dU = TdS + PdV dU = VdP - SdT dU = SdT + VdP The internal pressure ( U/ V) T for an ideal gas is: 0 P a/V 2 RT/V If the cold junction of a thermo-couple is kept at 0°C and the hot junction is kept at T°C then the relation between neutral temperature (T n) and temperature of inversion (T i) is T n = 2T i T n = T i - T T n = T i + T T n = T i/2 In a cyclic process, the change in internal energy ( U ) is always: Zero Positive Negative Dependent on the path A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U 1 , at wavelength 500 nm is U 2 and that at 1000 nm is U 3 . Wien's constant, b = 2.88 10 6 nmK . Which of the following is correct? U 1 = 0 U 3 = 0 U 1 > U 2 U 2 > U 1 A sample of 0.1 g of water at 100 C and normal pressure (1.013 10 5 Nm -2 ) requires 54 cal of heat energy to convert to steam at 100 C . If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is 42.2 J 208.7 J 104.3 J 84.5 J Two gases A and B are filled at the same pressure in separate cylinders with movable pistons of radius r A and r B , respectively. On supplying an equal amount of heat to both the systems reversibly under constant pressure, the pistons of gas A and B are displaced by 16 cm and 9 cm, respectively. If the change in their internal energy is the same, then the ratio r A r B is equal to 3 2 4 3 3 4 2 3 The relationship between H and U for the combustion of benzene C 6H 6(l) at 298 K is: H = U - 1.5RT H = U + 1.5RT H = U - 3RT H = U + 3RT For the combustion of 1 mole of liquid benzene ( C 6H 6 ) at 25 C , the difference H - U is: -3.71 kJ -7.42 kJ +3.71 kJ 0 kJ Which of the following Maxwell relations is correct? ( T/ V) s = -( P/ S) v ( T/ P) s = -( V/ S) p ( S/ V) t = -( P/ T) v ( V/ T) p = ( S/ P) t The average bond enthalpy of C=O in CO 2 is calculated using the enthalpy of formation of CO 2 ( -393.5 kJ/mol ), enthalpy of sublimation of C(s) ( 717 kJ/mol ), and bond energy of O=O ( 498 kJ/mol ). The value is approximately: 803.2 kJ/mol 1606.5 kJ/mol 401.6 kJ/mol 1210.5 kJ/mol A mixture contains 1 mole of Helium and 1 mole of Hydrogen gas ( H 2 ). The value of C p/C v for the mixture is: 1.53 1.40 1.67 1.50 A thermodynamic system undergoes a cyclic process such that the P-V graph is a circle of diameter 2 atm in pressure and 2 L in volume. The work done in one cycle is: L atm 2π L atm 4π L atm Zero The enthalpy of formation of OH -(aq) is determined from the heat of neutralization of a strong acid and base. Given Δ H f ∘[H 2O(l)] = -285.8 kJ/mol and Δ H neut = -57.1 kJ/mol , the Δ H f ∘[OH -(aq)] (taking Δ H f ∘[H +(aq)] = 0 ) is: -228.7 kJ/mol -342.9 kJ/mol -285.8 kJ/mol +57.1 kJ/mol